Comments on: How to Convert a String to an int in C++

By: JIm Anderson

JIm Anderson — Mon, 20 Aug 2018 12:59:00 +0000

In reply to jft. Fair enough!

By: jft

jft — Mon, 20 Aug 2018 12:04:00 +0000

“The if statement in the middle is horribly unreadable, and, as near as I
can tell, for no good reason. Granted, putting the decl of `n` inside
the if statement limits the scope of the variable, but that seems like a
tiny gain. Jamming three lines together seems unreadable.”

To quote a famous saying… One person’s meat is another person’s poison… 🙂

By: JIm Anderson

JIm Anderson — Sat, 18 Aug 2018 20:48:00 +0000

Thanks for the aritcle. It was interesting and educational, but I’d like to call you on the second example:

The if statement in the middle is horribly unreadable, and, as near as I can tell, for no good reason. Granted, putting the decl of `n` inside the if statement limits the scope of the variable, but that seems like a tiny gain. Jamming three lines together seems unreadable.

How about splitting it into:
str = last;
const auto n = strtoul(str), const_cast(&last), 10);
if (last != str)
nos.push_back(n);

I could well have missed something in this translation, but I tihnk that does the same thing, and doesn’t require the reader to stop and remember what the `;` operator does in the middle of an expression.

I really enjoyed this article, don’t get me wrong! I just got tripped up on this one. 😉

Thanks for writing this! I’m looking forward to reading the performance followup!

By: Jonathan Boccara

Jonathan Boccara — Fri, 27 Jul 2018 12:16:00 +0000

In reply to jft. Updated too, thanks.

By: jft

jft — Fri, 27 Jul 2018 11:50:00 +0000

In reply to Jonathan Boccara.

The updated coliru link is http://coliru.stacked-crooked.com/a/c9d1852be539aa44

By: Jonathan Boccara

Jonathan Boccara — Fri, 27 Jul 2018 11:13:00 +0000

In reply to jft. Updated in the body of the article

By: Bartlomiej Filipek

Bartlomiej Filipek — Fri, 27 Jul 2018 05:49:00 +0000

Thanks for the post!

I’d also add that from_chars* are locale-independent functions, so probably that’s why they can be optimized.

By: jft

jft — Thu, 26 Jul 2018 09:59:00 +0000

In reply to Jakob Truelsen.

Yes. But within the context of this blog ” we will dissect their usages with the
example of obtaining a vector of unsigned integers from a string, with
the numbers within the string separated by multiple spaces.”In this case the numbers are space terminated (including the last number) and so atol() or strtoul() work as expected.

However, this aspect of string_view should have been pointed out. Thanks for the clarification.

By: jft

jft — Thu, 26 Jul 2018 09:48:00 +0000

In reply to Vincent Zalzal. Sorry, no. It wasn't coded as the emphasis was on the performance.

By: Jakob Truelsen

Jakob Truelsen — Thu, 26 Jul 2018 07:24:00 +0000

I think the information in the Accepts std::string_view row is wrong. You cannot parse a string_view.data() to
atol() or strtoul(). As the returned data is not 0 terminated. Given the string “1234” we can create a string view of the first three chars, but parsing that to atol() does not yield 123 as expected but instead 1234.